Mike-
Two selling stations are a must, you just need them for those times you have two big movies, or when you've got a merchant sponsored kid show or something.People hate, to wait and will avoid the stand if they perceive tey will be waiting.
The soda machine should be centered in the front of the stand. I don't think you need more than one machine, remember you can get machines with as many heads as you need. You can have two of the same heads for the popular drinks. I would have a floor model popcorn warmer in the front. OR you could put the popper on the back counter in the middle of the two serving stations and omit the floor model warmer altogether. Personally, I would do both. Now the "candy case" as you put it could be done many different ways. Most new builds have a small "display box area". What I mean by that is that it displays the candies for sale only, it doesn't hold any of them, as they are kept in drawers behind the stand. So that is an option, just build the display box into the front of the stand, or another idea would be to have the candy case located somewhere in the front of the stand, or another idea, would be to just make your own nice looking display (a local independant in the area just glues the candy boxes to a piece of poster board,puts it on the back wall for all to see then keeps the candy in drawers behind the stand)I would probably do that (but make it look nicer, have a nice display box built and mounted on the back wall-that way everybody can see it, because if it is a case in the front, someone will almost always be standing in front of it.This way everybody is able to see it, and you can keep your candy in drawers in the stand. Counter top refrigerator for bottled juices, waters, ONE big, Superpretzel warmer with the shelves, for both pretzels and nachos, one Gehls bag-in box nacho cheese dispenser for the cheese for the same, hang cotton candy from chains mounted to the ceiling or along the back wall.One server products automatic butter machine on the front of the stand. Don't forget to leave plenty of room on the back of your stand for the tubs/bags. The soda cups/lids should be held by the soda machine in their own holders.Leave plenty of room for you to have enough stock on hand in the stand in locked cupboards,cups/tubs/bags/butter/cheese/salt/nacho chips/napkins/straws/etc...
One thing I can't say enough about it marketing...If people can see it, they will buy it, if you can make it look appealing and attractive, they will buy it. I am a firm believer in back lit signage, list all your items and prices, provide a couple of nice back lit pictures of nachos, or popcorn and a drink, etc. Get all of the advertising material from the suppliers, get those "Superpretzel" signs from J and J snack foods, get the nachos sign from Gehls cheese,get your cotton candy out there where people can see it, etc...
The best thing to do would be visit a few theatres, both independants, and chains, and see what others are doing, watch and learn from what they have done.Some companies also will show you pictures of some of the stands they have done, pretend your shopping around and take a look at those for some ideas.
This is the area of the theatre where the money is made, so it needs to be well thought out.
Good luck,
Jeff